This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This study will be a prospective cohort study conducted in the Emergency Department of Virginia Commonwealth University Health Systems/Medical College of Virginia Hospitals. We will attempt to enroll approximately 100-200 consecutive patients admitted to the Emergency Department (ED) with suspected pulmonary embolism. Exclusion criteria are incarceration and age younger then 18 years. Our aim is to determine the negative predictive value of the seven item questionnaire based on the Wells clinical model combined with the use of the readily available, inexpensive, reliable and quick immunoturbidimetric plasma D-dimer test as compared to CTA in the evaluation of ambulatory ED patients with suspected PE. We aim to prove the worth of these methods as effective screening tests in our patient populations so as to decrease the number of patients requiring CTA. Additional benefits include: more rapid disposition of selected ED patients;significant reduction in CTA procedures with resultant decrease in radiation exposure, use of intravenous contrast agents, and reduction of CT scanner procedure volume;improved utilization of diagnostic resources and ED personnel;potential cost savings with a more simplified diagnostic algorithm;and improved efficiency in the diagnosis and disposition of a currently complex patient population.